In a system in which a base station apparatus and a terminal perform radio communication, handover control is performed under which the terminal switches a connection between the neighbour base station apparatus in order to perform high-quality communication.
The handover may frequently occur for the terminal connected to the base station apparatus at an edge (cell edge) of a cell, which is a communicable range of the base station apparatus. Particularly, a phenomenon of frequent occurrence of the handover, namely, a phenomenon called ping-pong occurs when the terminal moves at a low speed.
For a high-speed terminal of which the moving speed is relatively high, a change of a propagation path is large, and a change of reception quality often occurs due to the large change of the propagation path. Thus, the probability of occurrence of the ping-pong is low. On the other hand, for a low-speed terminal of which the moving speed is relatively low, the change of the propagation path is small, and the change of the reception quality rarely occurs due to the small change of the propagation path. Thus, the probability of causing the ping-pong is high.
For example, NPL 1 discloses a radio communication system in which the base station apparatus determines the handover of the terminal to the neighbour base station apparatus based on reception quality information indicating the reception quality of the neighbour base station apparatus, which is measured by the terminal. According to the technique disclosed in NPL 1, a 3GPP standardization organization establishes a function in which the terminal waits the transmission of the reception quality information to the base station apparatus for a certain period of time (called time to trigger (hereinafter, referred to as TTT)) so that the handover does not frequently occur for the terminal connected to the base station apparatus at the cell edge.
A parameter deciding TTT is referred to as a mobility parameter. For the mobility parameter established by the 3GPP standardization organization, three ways of parameters, namely, a high-speed parameter, a medium-speed parameter longer than the high-speed parameter, and a low-speed parameter longer than the medium-speed parameter are set according to the moving speed of the terminal. The terminal sets the parameter corresponding to the moving speed of itself from the mobility parameter as the parameter determining the handover. The terminal waits the notification to the base station apparatus of the reception quality information for time indicated by the set parameter, and the terminal notifies the base station apparatus of the reception quality information after the time indicated by the parameter elapses.
The function enables the terminal to wait the transmission of the reception quality information according to the moving speed. For example, because the low-speed parameter is set relatively longer, repetition of the handover can be suppressed even if the low-speed terminal is located at the cell edge. Because the high-speed parameter is set relatively shorter, even if the high-speed terminal moves to an outside of the cell at high speed, it can avoid a delay in start of the handover to the neighbour base station apparatus and the disconnection of the connection.